1. Technical Field
This disclosure relates to an image forming apparatus to convey a recording medium to a sheet conveying path provided to an image forming part via a sheet reentry path for duplex copying when the recording medium has an image on a first surface thereof and no image on a second surface thereof.
2. Related Art
As an example of known image forming apparatus, some image forming apparatuses have a sheet reentry path for conveying a sheet as a recording medium having a first image formed on a first surface thereof for duplex copying for a second image to be formed on a second surface thereof.
For example, in a comparative image forming apparatus having the above-described configuration, a charger uniformly charges a photoconductor that rotates while being charged. Then, an optical writing device emits a light beam to irradiate the charged photoconductor, so that an electrostatic latent image is formed on the photoconductor. A developing device develops the electrostatic latent image formed on the photoconductor into a visible toner image. By so doing, the toner image is transferred onto a sheet conveyed between the photoconductor and a transfer device.
A sheet tray that is detachably attachable to an apparatus body contains the sheet therein so as to supply the sheet to an image forming part. The leading end of the sheet that is contained in the sheet tray is in contact with a sheet feed roller. As the sheet feed roller rotates, the sheet is fed to a sheet conveying path.
The sheet fed from the sheet tray is conveyed to a transfer nip region formed between the photoconductor and the transfer device of the image forming part. After the toner image formed on the photoconductor is transferred onto the sheet in the transfer nip region, the sheet is conveyed to a fixing device to fix the toner image to the sheet. Residual toner remaining on the photoconductor is removed by a cleaning blade that is disposed in contact with the photoconductor.
Thereafter, the sheet reaches a position where a switching claw is disposed to change its direction whether the sheet is discharged to an outside of the comparative image forming apparatus via a sheet discharging path or is conveyed to the sheet conveying path again via a sheet reversing unit and a sheet reentry path.
The sheet is conveyed to the sheet conveying path again for duplex printing and is reversed upside down in a sheet reversing unit. Then, the sheet is conveyed via the sheet reentry path disposed immediately above the sheet tray to the sheet conveying path. Then, when the sheet passes through the image forming part, a toner image is formed on the rear surface of the sheet. The toner image formed on the rear surface on the sheet is fixed to the sheet in the fixing device. Accordingly, the toner images are formed on both surfaces of the sheet.